Vehicles, such as trucks, typically have maximum load ratings set by the vehicle manufacturer. Many vehicles have payload areas that can be loaded with a payload that could exceed the maximum load rating. The payload areas can also be improperly loaded with a payload even though the payload doesn't exceed the maximum load rating for the vehicle. For example, a payload below the maximum load rating could be located too far to one side or too far to the rear, thereby changing the handling or steering characteristics of the vehicle. It is highly desirable to provide a warning system that indicates when a vehicle is improperly loaded.
Prior systems have been designed to accurately measure the payload weight or axle weight. Most of these systems use load cells to support the weight and provide an electrical signal indicative of the weight. Some systems have relied on the deflection of the vehicle's suspension to provide an indication of load. As an example, U.S. Pat. No. 3,531,766 to Henzel discloses such a sensing system for overload indication. U.S. Pat. Nos. 4,789,033; 5,522,468; and 6,259,041 B1 to Dohrmann show various systems that translate suspension travel into motion that can be measured. The sensor output is sent to a display unit that gives an indication of weight. These prior art systems, while detecting weight, have limitations in determining or detecting improper load conditions in a vehicle.